1. Field of the Invention
The present invention relates to a semiconductor circuit, a semiconductor device, a line break detection method, and a computer readable medium storing a line break detection program. The present invention particularly relates to a semiconductor circuit, semiconductor device, line break detection method, and computer readable medium storing a line break detection program, for monitoring battery voltages.
2. Description of the Related Art
A battery in which plural batteries (battery cells) are connected in series (as a specific example, a lithium ion battery or the like) is commonly used as a high power output battery with a large capacity, to be used for driving a motor of a hybrid automobile or an electric automobile, or the like. A battery monitoring system for monitoring and controlling voltages of the cells of the battery is known.
A conventional battery monitoring system is provided with a battery cell group, including plural battery cells, and a semiconductor circuit that measures and controls voltages of the battery cells included in the battery cell group.
In the conventional battery monitoring system, cell voltage equalization processing of the battery cell group (to make respective voltage values of the battery cells equal), charge/discharge control processing (control of charging and discharging of the battery cells), and the like, are carried out on the basis of voltage information of the battery cells that is obtained from the semiconductor circuit for measurement. In this battery monitoring system, if there is a line break in a signal line that connects a battery cell with the semiconductor circuit for measurement or suchlike, defect may arise in the battery monitoring system.
Accordingly, technologies for detecting a break in a signal line are known (Japanese Patent Application Laid-Open (JP-A) Nos. 2002-343445, 2001-116776, 2006-29923, 2004-170335, 2005-168118, 2004-104989, 2006-50784 and 2007-225484).
In the technologies recited in JP-A Nos. 2002-343445, 2001-116776 and 2006-29923, a resistance for detecting a line break is connected to between the battery cells, and a current from the battery cells always flows through this resistance. Therefore, in order to suppress a current during standby (a dark current), the resistance value must be made large. However, there are limitations on the resistance value and therefore may be difficult to suppress the dark current.
In the technologies recited in JP-A Nos. 2004-170335, 2005-168118, 2004-104989 and 2006-50784, an operation in which battery cells are short-circuited with a switch is required for detecting a line break. If the battery cells are not in an over-charged condition, this operation causes a discharge operation. As a result, battery voltages may become uneven between the battery cells.
In the technologies recited in JP-A Nos. 2004-170335 and 2007-225484, a battery voltage measurement circuit for measuring battery voltages, and a calculation device for calculating battery voltage differences, are required to determine whether there is a line break. In these technologies, plural voltages must be measured by the battery voltage measurement circuit and calculations performed by the calculation device. Consequently, these technologies may take time to detect a line break, and may be difficult to reduce the duration thereof. Moreover, it may be difficult for a semiconductor circuit in which only one battery voltage measurement circuit is provided to measure the battery cell voltages continuously during a line break detection period.